As communication capacity has increased in recent years, OADM (Optical Add Drop Multiplexer) devices that perform optical transmission according to the wavelength division multiplex (WDM) format have been introduced in the backbone and metro areas.
This OADM device is used, for example, for a bidirectional ring transmission path and has a function that branches/inserts an optical signal over the transmission path. Thus, the OADM device sets through (hereinafter abbreviated as THR) or ADD/DROP for each operational optical wavelength.
A related art reference of the present invention discloses a technique that restricts not only the number of wavelengths that can be used at a time on a particular incoming line but also the wavelength group that can be used at a time on a particular outgoing line at all edge nodes contained in a wavelength multiplex network that uses a network management device and a relay device so as to prevent optical fibers from being burnt and damaged (for example, refer to Patent Literature 1).
Another related art reference discloses a technique that controls connections to inter-carrier lines if an interconnecting gateway switch that performs switching and connection between different communication carriers detects passing calls under restriction such that the number of lines or ratio used for passing calls under restriction of inter-carrier lines becomes equal to or smaller than a predetermined number of lines or ratio (for example, refer to Patent Literature 2).